Synthesis of Nanocomposites of Polypropylene with Graphite Nanosheets by In Situ Polymerization Using a Fourth Generation Ziegler-Natta Catalyst

摘要

Polypropylene nanocomposites with expanded graphite nanosheets (xGN) were synthesized by in situ polymerization employing a Ziegler-Natta catalyst supported on particles of MgCl2 containing xGN (mass ratio 1: 1) and internal electron donor to control isotacticity, and their properties were compared with those of neat polypropylene obtained using a prepared standard Ziegler-Natta catalyst. SEM micrographs showed an alteration in the morphology of the catalyst with nanoparticles when compared with the standard one. It was noted that the catalyst containing xGN was more reactive for propylene polymerization than the standard one. By thermogravimetric analyses, it was detected that the PP/xGN nanocomposites showed higher thermal stability than PP. Differential scanning calorimetry (DSC) showed that the nanocomposites presented higher crystallinity degree, indicating that the nanofillers acted as nucleating agent. Scanning (SEM) and transmission (TEM) electron microscopies showed that the nanofillers were well dispersed into the PP matrix. By dynamic-mechanical analyses (DMA) it was observed an increase in glass transition temperature and the nanocomposites moduli.